In the final discussion of the afternoon, "Sustainable Development," the panel agreed that overall population growth itself isn't going to be the major influence on the state of the world's ecosystems. Rather, as ecologist Stuart Pimm of Duke University in Durham, North Carolina, explained, the greatest change in impact will come from the 1 billion people--think China--whose living standards are poised to rival those of North Americans. Cheap and clean energy won't necessarily obviate the impact, noted James Salzman of Duke University Law School in Durham, because other problems such as habitat destruction would remain. The big challenge will be how to deal with the interaction of multiple threats, said William Clark of Harvard University in Boston.